Hydrocarbon polymers which contain reactive functional groups are known in the art. For example, Japanese (Kokai) 7-102017 to Kanegafuchi Chemical Industry discloses the preparation of various polymers having terminal unsaturation by reacting the corresponding hydroxyl-terminated polymer with a compound selected from an allyl halide, an acrylic acid, an oxirane ring-containing compound having carbon-carbon double bonds or a compound containing an isocyanate group and carbon-carbon double bonds in its molecule. The starting polymer, which must contain at least 1.1 hydroxyl groups per molecule, can be prepared by carrying out a chain scission of the hydrocarbon polymer chain by reacting it with ozone, followed by reduction with lithium aluminum hydride. This method for producing the hydroxy-functional precursor polymer has a disadvantage in that the chain scission results in an undesirable reduction of polymer molecular weight, as observed in Reference Example 1 of the above mentioned Kanegafuchi publication.
In another approach, allylic functionality on polyisobutylene can be converted to hydroxyl by a hydroboration-oxidation sequence. This two-stage process employs treatment of the polymer with diborane or 9-borabicyclo{3.3.1}nonane (9-BBN), followed by reaction with hydrogen peroxide, to convert C.dbd.C groups to alcohol-containing groups. Hydroboration with diborane results in some secondary hydroxyl formation, whereas 9-BBN is highly regioselective and gives only primary alcohols. Thus, this technique may be used to prepare a polyisobutylene polymer having at least one end group of the formula --CH.sub.2 CH.sub.2 CH.sub.2 --OH. This hydroxyl group can, in turn, be reacted with, e.g., acryloyl chloride to provide a polymer having an end group of the formula EQU --CH.sub.2 CH.sub.2 CH.sub.2 --O--C(O)CH.dbd.CH.sub.2
Unlike polymers which contain vinylic unsaturation, acrylic-functional polymers are highly desirable since they can be readily cured by exposure to ultraviolet (UV) radiation when formulated with a photoinitiator. They therefore find utility in coating, ink and paint applications. However, even these systems have distinct disadvantages in that the hydroboration of allyl-functional polyisobutylene is difficult. In addition to being quite expensive, the boranes are flammable and react violently with water and are therefore hazardous. Furthermore, the above mentioned oxidation of the hydroboration product by H.sub.2 O.sub.2 adds to the complexity of this synthesis scheme.
There is therefore a need for an improved method for the production of acrylic-functional polyisobutylene (PIB), and corresponding copolymers of isobutylene, which are not plagued with the above drawbacks. Particularly, there is a need for telechelic (i.e., having two identical reactive end-groups) polymers such as telechelic acrylic-functional polyisobutylene. Such polymers having acrylic end groups can be reacted through chain extension and/or crosslinking schemes to produce cured compositions having a precise molecular weight between crosslinks, and therefore, more predictable and controllable properties than corresponding systems which contain randomly spaced reactive groups.